Fong-Jiao Hong

Bio: Fong-Jiao Hong is an academic researcher from University of Malaya. The author has contributed to research in topics: Electrophilic aromatic substitution & Substituent. The author has an hindex of 4, co-authored 4 publications receiving 62 citations.

Biomimetic oxidative dimerization of anodically generated stilbene radical cations: effect of aromatic substitution on product distribution and reaction pathways.

Abstract: A systematic study of the electrochemical oxidation of 1,2-diarylalkenes was carried out with the focus on detailed product studies and variation of product type as a function of aromatic substitution. A reinvestigation of the electrochemical oxidation of 4,4′-dimethoxystilbene under various conditions was first carried out, and all products formed were fully characterized and quantitated. This was followed by a systematic investigation of the effect of aromatic substitution on the nature and distribution of the products. The aromatic substituents were found to fall into three main categories, viz., substrates in which the nature and position of the aromatic substituents gave rise to essentially the same products as 4,4′-dimethoxystilbene, for example, tetraaryltetrahydrofurans, dehydrotetralins, and aldehydes (p-MeO or p-NMe2 on one ring and X on the other ring, where X = o-MeO or p-alkyl, or m- or p-EWG; e.g., 4-methoxy-4′-trifluoromethylstilbene); those that gave rise to a mixture of indanyl (or tetral...

Transformations of the 2,7-Seco Aspidosperma alkaloid leuconolam, structure revision of epi-leuconolam, and partial syntheses of leuconoxine and leuconodines A and F.

Abstract: Several transformations of the seco Aspidosperma alkaloid leuconolam were carried out. The based-induced reaction resulted in cyclization to yield two epimers, the major product corresponding to the optical antipode of a (+)-meloscine derivative. The structures and relative configuration of the products were confirmed by X-ray diffraction analysis. Reaction of leuconolam and epi-leuconolam with various acids, molecular bromine, and hydrogen gave results that indicated that the structure of the alkaloid, previously assigned as epi-leuconolam, was incorrect. This was confirmed by an X-ray diffraction analysis, which revealed that epi-leuconolam is in fact 6,7-dehydroleuconoxine. Short partial syntheses of the diazaspiro indole alkaloid leuconoxine and the new leuconoxine-type alkaloids leuconodines A and F were carried out.

Electrochemically Mediated Oxidative Transformations of Substituted 4-Methoxystilbenes: Effect of Ortho-Substituted Nucleophilic Groups.

Abstract: A systematic study was undertaken to determine the influence of ortho′-substituted nucleophilic groups (OH, NH2, or NHR) on the reactivity of anodically generated 4-methoxy- and 3,4-dimethoxystilbene cation radicals The results showed that when ortho-substituted nucleophilic groups such as OH and NHR are present in the other ring, both direct and crossover intramolecular cation–nucleophile reactions occur to give bisbenzofurans/bisindoles or fused bisbenzopyrans/bisquinolines, respectively Where an additional 3-methoxy substituent is present, bridged oxocine/azocine products are formed in addition to the bisbenzopyrans/bisquinolines and bisbenzofurans/bisindoles Mechanistic rationalization of the observed behavior is presented based on a generalized pathway involving fast cation radical dimerization following electron transfer, followed by direct and crossover trapping of the benzylic cations by the ortho-substituted oxygen and nitrogen nucleophilic groups In the instances where an additional 3-methox

Transformations of Ferric Chloride-Generated Stilbene Cation Radicals. The Effect of Aromatic Substitution and a Comparison with Anodic Oxidation.

Abstract: A systematic study on the FeCl3-induced oxidation of 1,2-diarylalkenes was carried out with the focus on the variation of product type as a function of aromatic substitution, as well as to compare the reactivity of stilbene cation radicals generated via FeIII oxidation with those generated by anodic oxidation. The aromatic substituents were found to fall into three main categories, namely those that give rise to tetralins and/or dehydrotetralins, those that give products possessing pallidol and ampelopsin F-type carbon skeletons, and last, those that give rise to trimeric products, indanes, and dehydrotetralins/tetralins. The latter are those stilbenes with a para-methoxy substituent in one ring and a para- or meta-EWG (CF3, NO2, Cl, F) in the other, and represent the most prominent departure when compared with the behavior of the same stilbenes under the conditions of anodic oxidation. Reaction pathways to rationalize the formation of the different products are presented.

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

Abstract: Electrochemistry represents one of the most intimate ways of interacting with molecules. This review discusses advances in synthetic organic electrochemistry since 2000. Enabling methods and synthetic applications are analyzed alongside innate advantages as well as future challenges of electroorganic chemistry.

Chemistry and Biology of Resveratrol-Derived Natural Products

Abstract: Since the dawn of the 20th century, the average life expectancy at birth has nearly doubled due to advances in science and medicine. As medical records grew more reliable, it became apparent that, while overall life span was increasing, there were significant epidemiological differences between geographical regions, with people from countries such as Japan, France, and Switzerland enjoying longer life expectancy as compared to other regions of the world. The causative factors for these disparities in both mortality and morbidity have been attributed not only to genetics but also to the contributions of highly variable lifestyle and environmental influences.1 Barring differences in modernization and public health policy, diet is the most significant epidemiological factor cross-culturally and is thought to be a profoundly important contributor to health and overall well-being. Prior to the early 1990s, there was a general consensus in support of the belief that moderate alcohol consumption significantly lowered the risk of coronary heart disease (CHD).2 However, it was not clear whether this was true of all alcoholic beverages or which constituents in the drinks were responsible for these beneficial properties.3 In 1992, Siemann and Creasy4 reported that resveratrol (1) was present in significant concentrations in red wine, drawing attention to the fact that it was also an active principle found in Japanese and Chinese folk medicines used to treat ailments related to the liver, skin, heart, and lipid metabolism.5 The discovery of resveratrol in wine was particularly timely; although the correlation between high fat and cholesterol consumption and coronary heart disease was widely accepted,6 certain populations, namely the French, had a low incidence of CHD mortality despite a diet and lifestyle that exposed these individuals to elevated risk factors.7 The cardioprotective ability of resveratrol, its oligomers, along with other phytochemicals present in wine, appeared to resolve this “French Paradox” and advanced the notion that a chemical constituent of one’s diet could be beneficial to health.8 Although the reality of the French Paradox remains contentious,9,10 research into the health benefits of resveratrol has exploded as a result. The reported biological activities of resveratrol are numerous, including antioxidant,11 anticancer,12 antidiabetic,13,14 cardioprotective,15 and even antiaging properties,16 to name a few. The body of literature regarding the biological activity of resveratrol is expansive and beyond of the scope of this review. We invite the readers to the following resources for background on this exciting and ongoing field of research.17−21 Despite its enormous popularity, resveratrol is but a single compound in a large, structurally diverse class of oligomeric stilbenoids that are present in the wines and foods that we consume.22,23 Until recently, access to these oligomeric natural products was limited to isolation from natural sources, which severely hampered their biological evaluation. The scientific interest in resveratrol has undoubtedly instigated the renewed attention in these compounds by the chemical community. Advances in the characterization, isolation techniques, and synthesis of these natural products have significantly enriched our understanding of their chemistry and biology. Our review seeks to document the history and recent progress in the isolation, chemical synthesis, and biology of this fascinating class of phytochemicals, while providing new insight on the biosynthesis and future prospects for the field as a whole.

Total Syntheses of (−)-Mersicarpine, (−)-Scholarisine G, (+)-Melodinine E, (−)-Leuconoxine, (−)-Leuconolam, (−)-Leuconodine A, (+)-Leuconodine F, and (−)-Leuconodine C: Self-Induced Diastereomeric Anisochronism (SIDA) Phenomenon for Scholarisine G and Leuconodines A and C

Abstract: Enantioselective total syntheses of title natural products from a common cyclohexenone derivative (S)-18 were reported. Ozonolysis of (S)-18 afforded a stable diketo ester (R)-17 that was subsequently converted to two skeletally different natural products, i.e., (−)-mersicarpine (8) with a [6.5.6.7] fused tetracyclic ring system and (−)-scholarisine G (9) with a [6.5.6.6.5] fused pentacyclic skeleton, respectively. The postcyclization diversification was realized by taking advantage of the facile conversion of (+)-melodinine E (6) to N-acyliminium ion 7, from which a hydroxy group was selectively introduced to the C6, C7, C10 and the central C21 position of diazafenestrane system, leading to (−)-leuconodine A (11), (+)-leuconodine F (12), (−)-scholarisine G (9), (−)-leuconodine C (13), and skeletally different (−)-leuconolam (5). Furthermore, an unprecedented non-natural oxabridged oxadiazafenestrane 68 was formed by oxidation of (+)-melodinine E (6). During the course of this study, a strong self-induced...